EP0893627B1 - Steuersystem für stufenloses Getriebe - Google Patents

Steuersystem für stufenloses Getriebe Download PDF

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Publication number
EP0893627B1
EP0893627B1 EP98113895A EP98113895A EP0893627B1 EP 0893627 B1 EP0893627 B1 EP 0893627B1 EP 98113895 A EP98113895 A EP 98113895A EP 98113895 A EP98113895 A EP 98113895A EP 0893627 B1 EP0893627 B1 EP 0893627B1
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EP
European Patent Office
Prior art keywords
line pressure
control
microcomputer
pressure
control system
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Application number
EP98113895A
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English (en)
French (fr)
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EP0893627A2 (de
EP0893627A3 (de
Inventor
Makoto Sawada
Hirofumi Okahara
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Nissan Motor Co Ltd
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Nissan Motor Co Ltd
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Publication of EP0893627A3 publication Critical patent/EP0893627A3/de
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16H—GEARING
    • F16H61/00—Control functions within control units of change-speed- or reversing-gearings for conveying rotary motion ; Control of exclusively fluid gearing, friction gearing, gearings with endless flexible members or other particular types of gearing
    • F16H61/66—Control functions within control units of change-speed- or reversing-gearings for conveying rotary motion ; Control of exclusively fluid gearing, friction gearing, gearings with endless flexible members or other particular types of gearing specially adapted for continuously variable gearings
    • F16H61/662—Control functions within control units of change-speed- or reversing-gearings for conveying rotary motion ; Control of exclusively fluid gearing, friction gearing, gearings with endless flexible members or other particular types of gearing specially adapted for continuously variable gearings with endless flexible members
    • F16H61/66272—Control functions within control units of change-speed- or reversing-gearings for conveying rotary motion ; Control of exclusively fluid gearing, friction gearing, gearings with endless flexible members or other particular types of gearing specially adapted for continuously variable gearings with endless flexible members characterised by means for controlling the torque transmitting capability of the gearing
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16H—GEARING
    • F16H59/00—Control inputs to control units of change-speed-, or reversing-gearings for conveying rotary motion
    • F16H59/36—Inputs being a function of speed
    • F16H59/46—Inputs being a function of speed dependent on a comparison between speeds
    • F16H2059/465—Detecting slip, e.g. clutch slip ratio
    • F16H2059/467—Detecting slip, e.g. clutch slip ratio of torque converter
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16H—GEARING
    • F16H61/00—Control functions within control units of change-speed- or reversing-gearings for conveying rotary motion ; Control of exclusively fluid gearing, friction gearing, gearings with endless flexible members or other particular types of gearing
    • F16H61/66—Control functions within control units of change-speed- or reversing-gearings for conveying rotary motion ; Control of exclusively fluid gearing, friction gearing, gearings with endless flexible members or other particular types of gearing specially adapted for continuously variable gearings
    • F16H61/662—Control functions within control units of change-speed- or reversing-gearings for conveying rotary motion ; Control of exclusively fluid gearing, friction gearing, gearings with endless flexible members or other particular types of gearing specially adapted for continuously variable gearings with endless flexible members
    • F16H61/66272—Control functions within control units of change-speed- or reversing-gearings for conveying rotary motion ; Control of exclusively fluid gearing, friction gearing, gearings with endless flexible members or other particular types of gearing specially adapted for continuously variable gearings with endless flexible members characterised by means for controlling the torque transmitting capability of the gearing
    • F16H2061/66281—Control functions within control units of change-speed- or reversing-gearings for conveying rotary motion ; Control of exclusively fluid gearing, friction gearing, gearings with endless flexible members or other particular types of gearing specially adapted for continuously variable gearings with endless flexible members characterised by means for controlling the torque transmitting capability of the gearing by increasing the line pressure at the occurrence of input torque peak

Definitions

  • the present Invention relates to improvements in a control system for a continuously variable transmission (CVT) for a vehicle, and more particularly to a control system of a belt type CVT.
  • CVT continuously variable transmission
  • a Japanese Patent Provisional Publication No. 8-200461 discloses a typical belt type CVT which comprises driver and follower pulleys and a belt for intercoupling the pulleys.
  • Each of the driver and follower pulleys has a variable groove at which the belt is held.
  • a belt holding force for holding the belt by each pulley is varied basically according to a line pressure which is produced by pressurizing a fluid by means of a pump through a CVT pressure control valve.
  • the line pressure is increased according to the Increase of an input load applied from an engine to the CVT.
  • the input load is basically calculated from a throttle opening and an engine revolution speed of an engine.
  • a clutch pressure for controlling a start dutch such as a forward clutch and a reverse brake disposed between the engine and the CVT is produced from a branch pressure of the line pressure and is controlled by means of a clutch pressure control valve to establish the engagement between the engine and the CVT.
  • US-A-4 734 082 according to the precharacterizing part of claim 1 discloses a control system for a continuously variable transmission of a vehicle wherein the continuously variable transmission comprises a driver pulley, a follower pulley and a belt intercoupling the pulleys.
  • the control system comprises a control circuit for applying a line pressure to the pulley according to an input load from the engine to the continuously variable transmission.
  • a driver pulley speed sensor, an engine speed sensor and a throttle valve position sensor are provided in order to detect a condition of the vehicle.
  • the throttle position sensor detects a temporally increased input load.
  • a correction section is provided for temporally increasing the line pressure when the input load is temporally increased.
  • a line pressure lowering speed regulator is provided for slowly decompressing the temporally increased line pressure.
  • the input load to the CVT mechanism is basically applied from the engine the input load is temporally increased by various reasons. For example, when an acceleration pedal is quickly and largely depressed, when a braking force is applied to the driving wheel according to the depression of a brake pedal, or when an intentional downshift is executed by the operation of a selector lever, the input load is temporally increased. In order to prevent the slippage of the belt even when the temporal increase of the input torque is generated, the conventional CVT is arranged to temporally correct the line pressure to adapt to such situation. These input load temporally increased conditions are detected from vehicle conditions caused by the operation of a driver. Therefore, it is possible to correctly increase the line pressure according to the detected condition.
  • the line pressure is increased in order to quickly increase the start clutch pressure to enable the engagement of the start clutch. That is, the line pressure is temporally increased when the select lever is set at a start shift position. After this temporal increase of the line pressure, the increased line pressure is held for a predetermined time and is steppingly and quickly decompressed to the normal line pressure.
  • a control system is for a continuously variable transmission (CVT) of a vehicle.
  • the CVT comprises a driver pulley, a follower pulley and a belt intercoupling the pulleys, and varies a transmission ratio by changing effective diameters of the pulleys.
  • the control system comprises a line pressure applying means, a vehicle condition detecting means, a temporal increase determining means, a pressure increasing means, and a slow decompressing means.
  • the line pressure applying means applies a line pressure to the pulleys according to an input load from the engine.
  • the vehicle condition detecting means detects a condition of the vehicle.
  • the temporal increase determining means determines according to the detected vehicle condition that the input load is temporally increased.
  • the pressure increasing means temporally increases the line pressure when the input load is temporally increased.
  • the slow decompressing means slowly decompresses the temporally increased line pressure after the line pressure is increased by the pressure increasing means.
  • the slow decompressing means decreases a decompression speed indicative of a speed of the decompression of the increased pressure according to an increase of the transmission ratio of the CVT.
  • FIG. 20B there is shown an embodiment of a control system for a continuously variable transmission (CVT) in accordance with the present invention.
  • CVT continuously variable transmission
  • Fig. 1 shows an embodiment of the CVT and the control system thereof according to the present invention.
  • a power transmission mechanism of the CVT is basically the same as that of a power transmission mechanism disclosed in a U.S. Patent No. 5,697,866 except that a torque converter 12 is employed instead of a fluid coupling and except that an anti-skid control system is employed in the vehicle equipped with the CVT. Therefore, the same parts and elements of the power transmission mechanism are designated by same reference numerals, and only a brief explanation thereof will be given hereinafter.
  • an engine 10 is connected to a V-belt type CVT mechanism 29 through the torque converter 12 and a forward/reverse change over mechanism 15.
  • An output shaft of the CVT mechanism 29 is connected to a differential unit 56.
  • These elements 10, 12, 29 and 56 constitute a so-called drive system.
  • the drive system transmits rotation of an output shaft 10a of the engine 10 to right and left drive shaft 66 and 68 at a selected speed ratio in a selected rotational direction to drive a vehicle.
  • a throttle valve 19 is disposed in an air intake passage 11 of the engine 10 and is arranged to change a degree of its opening in response to a depression degree of an accelerator pedal (no numeral).
  • a throttle opening sensor 303 is installed to the throttle valve 19 to detect a throttle opening TVO of the throttle valve 19 and to output a signal indicative of the throttle opening TVO.
  • An engine revolution speed sensor 301 is installed on the output shaft 10a of the engine 10 to detect an engine revolution speed N E and to output a signal indicative of the engine revolution speed N E .
  • the engine 10 is connected to an engine control unit 200 by which various engine operation factors such as fuel injection amount and timing and ignition timing are controlled so as to put the engine 10 in an optimum operating condition according to the running condition of the vehicle and a driver's intent.
  • the throttle opening indicative signal TVO outputted from the throttle opening sensor 303 also corresponds to the magnitude of the depression degree of the accelerator pedal.
  • the engine revolution speed sensor 301 is arranged to detect the rotation speed of the output shaft 10a of the engine 10 in this embodiment, it will be understood that it may be arranged to count the number of ignition pulses of the engine 10 as an engine revolution speed.
  • the torque converter 12 of this drive system is a lockup torque converter of a known type.
  • This lockup torque converter 12 comprises a pump impeller (input member) 12c, a turbine runner or turbine (output member) 12d, a stator 12e, and a lockup facing member (or lockup clutch) 12f for providing a direct mechanical drive by directly coupling the input and output members 12c and 12d.
  • the lockup facing member 12f is connected with an output shaft (turbine shaft) 13.
  • the lockup facing member 12d separates an apply side fluid chamber 12a and a release side fluid chamber 12b.
  • the release chamber 12b is formed between a cover 12g of a torque converter 12 and the lockup facing member 12f, and the apply chamber 12a is disposed on the opposite side of the lockup facing member 12f.
  • the apply chamber 12a When a fluid pressure is supplied into the apply chamber 12a, the lockup facing member 12f is pressed against the cover 12g, and the torque converter 12 is put in a lockup state in which the input member 12c and the output member 12d are directly connected.
  • the lockup facing member 12f is disengaged from the cover 12g, and the torque converter 12 is held in a non-lockup state (or unlockup state).
  • the fluid pressure supplied to the release chamber 12b is drained through the apply chamber 12a.
  • An input rotation speed sensor 305 is installed on an output shaft 13 (turbine output shaft) of the torque converter 12 as a drive system rotation condition change detecting means (estimated rotational change condition detecting means) in order to detect an input rotation speed of the CVT mechanism 29.
  • the forward clutch 40 When the vehicle is put in a normal running condition, the forward clutch 40 is put in a full engagement state. Therefore, the rotation speed of the turbine output shaft 13 is used as an input rotation speed N Pri of the CVT mechanism 29.
  • the forward/reverse change over mechanism 15 functions to control a creep running force by variably adjusting the engagement force of the forward clutch 40.
  • the fluid supplied to the release chamber 12b is drained through the apply chamber 12a to a reservoir 130, and a drained fluid of the fluid supplied to the apply chamber 12c is supplied from the release chamber 12b to other cooling and lubricating systems. That is, the selecting control between the lockup state and the unlockup state is executed by changing a flow direction of the fluid supplied to the lockup mechanism of the torque converter 12 as mentioned above without changing the fluid passage.
  • the forward/reverse drive direction change over mechanism 15 comprises a planetary gear system 17, the forward clutch 40 and a reverse brake 50.
  • the planetary gear system 17 comprises multistage pinion trains and a pinion carrier supporting these pinion trains.
  • the pinion carrier is connected to the driver pulley 16 of the CVT mechanism.29 through the driver pulley shaft 14, and a sun gear is connected to the turbine rotation shaft 13.
  • the pinion carrier is engageable with the turbine rotation shaft 13 by means of the forward clutch 40.
  • a ring gear of the planetary gear system 17 is engageable with a stationary housing.
  • the reverse brake 50 is disposed between a ring gear of the planetary gear system 17 and a stationary housing to hold the ring gear.
  • the forward clutch 40 When the forward clutch 40 is put in the engaged state by the supply of the fluid pressure to a fluid chamber 40a, the driver pulley shaft 14 and the turbine output shaft 13 are rotated in the same direction with equal speed through a pinion carrier.
  • the reverse brake 50 When the reverse brake 50 is engaged by the supply of the fluid pressure to the fluid chamber 50a, the driver pulley shaft 14 and the turbine output shaft 13 are rotated with equal speed but in the opposite direction.
  • the V-belt CVT mechanism 29 comprises a driver pulley 16, a follower (or driven) pulley 26, and a V-belt 24 for transmitting power between the pulleys.
  • the driver pulley 16 is mounted on the driver pulley shaft 14.
  • the driver pulley 16 comprises an axially stationary fixed conical disk 18, and an axially movable conical disk 22, which confront each other and define a V-shaped pulley groove therebetween for receiving the V-belt 24.
  • the fixed disk 18 rotates as a unit with the driver shaft 14.
  • the movable disk 22 is axially movable.
  • the follower pulley 26 is mounted on a follower pulley shaft 28.
  • the follower pulley 26 comprises an axially stationary fixed conical disk 30, a follower pulley cylinder chamber 32, and an axially movable conical disk 34.
  • the fixed and movable disks 30 and 34 confront each other and define a V-shaped pulley groove for receiving the V belt 24.
  • the fixed disk 30 rotates as a unit with the follower shaft 28.
  • the movable disk 34 is axially movable in dependence on a fluid pressure in the follower pulley cylinder chamber 32.
  • the V-belt CVT mechanism 29 further comprises a stepping motor 108 controlled by a transmission control unit 300.
  • a pinion 108a is connected to a rotation shaft of the stepping motor 108 and is meshed with a rack 182.
  • An end of the rack 182 and the movable conical disk 22 are interconnected through a lever 178.
  • the stepping motor 108 according to the drive signal D S/M from the transmission control unit 300, the movable conical disk 22 of the driver pulley 16 and the movable conical disk 34 of the follower pulley 26 are axially moved to vary the effective radius of the contact position of each pulley of the driver and follower pulleys 16 and 26 axially.
  • the CVT mechanism 29 can vary the speed ratio (transmission ratio or pulley ratio) between the driver pulley 16 and the follower pulley 26.
  • the shift control system (pulley ratio varying control) is generally arranged to vary the pulley groove width of one of the driver and follower pulleys and allow the groove width of the other to be adjusted automatically.
  • the arrangement is achieved by the belt of a push type which transmits the driving force mainly in the pushing direction.
  • the push type V-belt 24 comprises a set of plates which are overlappingly arranged in the longitudinal direction or wound direction of the belt.
  • a drive gear 46 fixed to the follower pulley shaft 28 is meshed with an idler gear 48 formed on an idler shaft 52.
  • a pinion gear 54 formed on the idler shaft 52 is meshed with a final gear 44 with which right and left drive shafts 66 and 68 are interconnected through the differential unit 56.
  • a vehicle speed sensor 302 is installed on this final output shaft to detect a vehicle speed V SP and output a signal indicative of the vehicle speed V SP to the transmission control unit 300.
  • the hydraulic pressure control apparatus comprises a pump 101 driven by the engine 10.
  • the pump 101 draws a working fluid from a reservoir 130 and supplies the fluid to an actuator unit 100 while applying a sufficient pressure to the fluid.
  • the construction of the actuator unit 100 is basically the same as that of the actuator unit disclosed in a U.S. Patent No. 5,697,866. Therefore, the same parts and elements are designated by same reference numerals, and only a brief explanation thereof will be given hereinafter.
  • a manual valve 104 is directly operated by a selector lever 103 so as to switchingly control a clutch pressure P CL to a cylinder chamber 40a of the forward clutch 40 and a brake pressure P BRK to a cylinder chamber 50a of the reverse brake 50.
  • An inhibitor switch 304 installed on the selector lever 103 detects a shift position selected by the selector lever 103 and outputs a shift range signal S RANGE indicative of the selected shift position. More particularly, the shift range signal S RANGE includes signals corresponding to P, R, N, D, 2, L according to the actually selected shift position.
  • a shift control valve 106 is controlled according to a relative displacement between the stepping motor 108 and the movable conical disk 22 of the driver pulley 16, more particularly it is controlled according to the movement of the lever 178. That is, the shift control valve 106 controls the fluid pressure (line pressure) P L(Pri) supplied to the driver pulley 16 according to a relative relationship between the required transmission ratio and a groove width of the driver pulley 16.
  • a lockup control duty valve 128 controls a lockup mechanism of the torque converter 12 so as to put the torque converter 12 in one of a lockup state and an unlockup state.
  • a transmission control unit 300 outputs a drive signal D L/U to the lockup control valve 128 to operate the lockup mechanism of the torque converter 12. More particularly, when the drive signal D L/U indicative a large duty ratio is outputted to the lockup control duty valve 128, the torque converter 12 is put in the lockup state. When the drive signal D L/U indicative of a small duty ratio is outputted to the lockup control valve 128, the torque converter 12 is put in the unlockup (non-lockup) state.
  • a clutch engagement duty valve 129 controls an engagement force for one of the forward clutch 40 and the reverse brake 50 according to a drive signal D CL from the transmission control unit 300.
  • a drive signal D CL indicates a large duty ratio
  • one of the forward clutch 40 and the reverse brake 50 is engaged.
  • the drive signal D CL indicates a small duty ratio, it is disengaged.
  • a line pressure control duty valve 120 controls the line pressure P L supplied mainly to the follower pulley 26 and partly to the driver pulley 16 so as to hold the belt 24 by the pulleys 26, 16 according to a drive signal D PL from the transmission control unit 300.
  • This duty valve 120 is represented as a modifier duty valve in the above cited Patent document.
  • the reason for this is the output pressure from the duty vale 120 once functions as a pilot pressure of a pilot pressure control valve named as a pressure modifier valve.
  • an output pressure from the pressure modifier valve functions as a pilot pressure of the line pressure control valve so as to control the line pressure P L produced in an upstream side of the line pressure control valve. That is, by controlling the duty ratio of the duty valve 120, the line pressure P L is indirectly controlled.
  • the objective line pressure P L(OR) is linearly increased according to the increase of the control signal to the line pressure control duty valve 120 or duty ratio D/T PL of the drive signal except for dead zone as shown in Fig. 2. More particularly, when the output pressure of the pressure modifier valve is increased, the base (original) pressure of the clutch pressure and the base pressure of the lockup pressure of the torque converter 12 are simultaneously increased although the gradients and intercepts thereof are different respectively from others.
  • the transmission control unit 300 comprises a microcomputer 310 functioning as a control means, and four drive circuits 311 to 314.
  • the microcomputer 310 outputs control signals for controlling the CVT mechanism 29 and the actuator unit 100 by executing a process shown by a flowchart of Fig. 3.
  • the first to fourth drive circuits 311 to 314 respectively convert the control signals outputted from the microcomputer 310 into drive signals for practically controlling the actuators such as the stepping motor 108 and the respective duty valves 120, 128 and 129.
  • the microcomputer 310 comprises an input interface circuit 310a including an A/D converter, a calculation processor 310b such as a microprocessor, a storage device 310c such as ROM and RAM, and an output interface circuit 310d including a D/A converter.
  • a calculation processor 310b such as a microprocessor
  • a storage device 310c such as ROM and RAM
  • an output interface circuit 310d including a D/A converter.
  • the microcomputer 310 executes various operations such as obtaining a rotation angle of the stepping motor 108 for setting the actual transmission ratio, outputting a pulse signal S S/M for achieving the rotation angle, obtaining the optimum line pressure for holding the belt 24, calculating the duty ratio D/T PL of the line pressure control duty valve 120 for achieving the necessary line pressure P L , obtaining the fluid pressure (torque converter pressure) P T/C for controlling the lockup mechanism of the torque converter 12, calculating the duty ratio D/T L/U of the lockup control duty valve 128 for achieving the torque converter pressure P T/C , outputting a lockup control signal S L/U according to the lockup control duty ratio D/T L/U , obtaining the fluid pressure (clutch pressure) P CL which is optimum to execute a creep running of the vehicle under when the accelerator pedal is put in the off condition (a foot of an operator is released from the accelerator pedal), calculating a duty ratio D/T CL of the clutch engagement control duty valve 129 necessary for achieving the required clutch pressure
  • the first drive circuit 311 converts the pulse control signal S S/M into a drive signal D S/M and outputs it to the stepping motor 108.
  • the second drive circuit 312 converts the pulse control signal S PL into a drive signal D PL and outputs it to the line pressure control duty valve 120.
  • the third drive circuit 313 converts the pulse control signal S L/U into a drive signal D L/U and outputs it to the lockup control duty valve 128.
  • the forth drive circuit 314 converts the pulse control signal S CL into a drive signal D CL and outputs it to the clutch engagement control duty valve 129. If the control signals according to the duty ratio and the pulse control signals satisfactorily indicate the desired duty ratios and number of pulses, the drive circuits 311 to 314 simply execute the amplifications thereof.
  • the engine control unit 200 also comprises a microcomputer which is interconnected with the microcomputer 310 of the transmission control unit 300 such that the engine 10 and the CVT are controlled according to the vehicle running condition.
  • the anti-skid control unit comprises an anti-skid control unit 500, first to fourth wheel speed sensors 501 to 504, a brake switch 505, an actuator unit 510 and first to fourth wheel cylinders 511 to 514.
  • the first to fourth wheel speed sensors 501 to 504 respectively detect wheel speeds V WFL , V WFR , V WRL and V WRR of four wheels of the vehicle and output wheel speed indicative signals to the anti-skid control unit 500.
  • the brake switch 505 detects that the brake pedal is depressed in a predetermined degree and outputs a detection signal indicative of the depression of the brake pedal to the anti-skid control unit 500.
  • the anti-skid control unit 500 comprises a microcomputer and outputs control signals to the actuator unit 510 to control the hydraulic pressures of the wheel cylinders 511 to 514 by executing various calculations such as calculating processes shown in Japanese Patent Provisional Publication No. 8-324415.
  • the actuator unit 510 comprises a plurality of electromagnetic valves for compressing and decompressing fluid pressures in the wheel cylinders 511 to 514 according to the control signals from the anti-skid control unit 510.
  • the braked wheel tends to be put in a lock state.
  • the pressure in the wheel cylinder of the braked wheel is decreased to increase the wheel speed by means of a reaction force from a road surface.
  • the pressure of the wheel cylinder of the braked wheel is slightly and steppingly increased. That is, the braking force is increased by the slow compression to ensure the vehicle deceleration speed and the brake distance. If the braking force becomes too large due to this slow compression, the decompression is again executed. That is, by repeating the decompression and the slow compression, both of the steering characteristics and the braking distance are kept good.
  • the microcomputer of the anti-skid control unit 500 is interconnected with the microcomputer 310 fo the transmission control unit 300, such that the transmission control unit 300 recognizes the controls and the detection signals of the anti-skid control unit 500.
  • the transmission control of the present embodiment will be discussed with reference to a calculating process shown by a flowchart of Fig. 3 which is executed by the microcomputer 310.
  • This calculating process is basically executed when the D-range is selected and when the engine control unit 200 requires no process to the transmission control unit 300.
  • This calculating process is implemented as a timer interruption process at predetermined sampling time ⁇ T such as 10 milliseconds (msec).
  • ⁇ T sampling time
  • the transmission control unit 300 timely executes a process for reading programs, maps and data used in the processor 310b from the storage device 310c and properly updates data calculated at the processor 310b and stores it in the storage device 310c.
  • the microcomputer 310 reads the signals indicative of the vehicle speed V SP outputted from the vehicle speed sensor 302, the engine revolution speed N E outputted from the engine revolution sensor 301, the input rotation speed N Pri outputted from the input rotation speed sensor 305, a throttle opening TVO outputted from the throttle opening sensor 303 and a shift range signal S RANGE form the inhibitor switch 304.
  • the microcomputer 310 calculates the engine torque T E on the basis of the throttle opening TVO and the engine revolution speed N E by executing an independently provided process (sub routine) such as a retrieval of a control map. More particularly, the present engine torque T E is obtained from the output characteristic map shown in Fig. 4 according to the throttle opening TVO and the engine revolution speed N E .
  • the microcomputer 310 executes a lockup control by jumping the routine to an independently provided process (subroutine). More particularly, a lockup speed V ON and an unlockup speed V OFF are determined by using a control map shown in Fig. 5 according to the vehicle speed V SP and the throttle opening TVO. Basically, when the vehicle speed V SP is greater than the lockup speed V ON , the microcomputer 310 generates and outputs the control signal S L/U including a lockup command for putting the torque converter 12 into the lockup state. When smaller than the unlockup speed V OFF , the microcomputer 310 generates and outputs the control signal S L/U including an unlockup command for putting the torque converter 12 into the unlockup state.
  • a gain employed for increasing the duty ratio D/T L/U is increased according to the magnitude of the difference.
  • the gain for increasing the duty ratio D/T L/U is decreased so as to buffer shift shocks caused by the transition to the full lockup state.
  • the microcomputer 310 calculates a goal transmission ratio C D by executing an independently provided process (subroutine) such as the retrieval of a control map.
  • the goal transmission ratio C D is the most ideal transmission ratio for achieving the present engine revolution speed N E from the vehicle speed and the throttle opening TVO. More particularly, as shown in Fig. 6, if a transmission ratio C, by which the vehicle speed V SP , the throttle opening TVO and the engine revolution speed N E are completely matched, is set, it is possible to ensure an acceleration according to the depression degree of the accelerator pedal (the throttle opening TVO) while satisfying the vehicle speed V SP and the engine revolution speed N E .
  • a straight line crossing with an origin point and having a constant gradient is a constant transmission ratio.
  • a straight line having the largest gradient in the whole area of the shift pattern is the largest speed reduction ratio of the vehicle, that is, a maximum transmission ratio C LO .
  • a straight line having the smallest gradient in the whole area of the shift pattern is the smallest speed reduction ratio of the vehicle, that is, a minimum transmission ratio C DH1 .
  • the shift control is implemented within an area from the maximum transmission ratio C LO to a 2-range minimum transmission ratio C 2Hi .
  • the microcomputer 310 calculates the objective transmission ratio C R according to an individually prepared process (subroutine). More particularly, when the goal transmission ratio C D is greater than the present transmission ratio C P , the objective transmission ratio C R is set to execute the downshift. When smaller than the present transmission ratio C P , the objective transmission ratio C R is set to execute the upshift. For example, the objective transmission ratio C R is set at a transmission ratio obtained at a moment elapsing a predetermined sampling time ⁇ T from when the shifting is executed from the present transmission ratio C P by the highest shift speed dC R /dt or smallest time constant ⁇ .
  • the throttle opening TVO is decreased from a nearly full open state, that is, when the depression degree of the accelerator pedal is decreased, the shift speed dC R /dt is little decreased or the time constant ⁇ is little increased. Further, when the throttle opening TVO is further quickly decreased, such that the depression of the accelerator pedal is cancelled, the shift speed dC R /dt is further decreased or the time constant ⁇ is further increased. That is to say, the objective transmission ratio C R is changed according to the closing change amount of the throttle valve 19.
  • the time constant ⁇ is employed in order to set the objective transmission ratio C R , that is, to control the shift speed. Therefore, when the goal transmission ratio C D is set, the objective transmission ratio C R is determined as a curve which takes values gradually converging to the goal transmission ratio C D .
  • the microcomputer 310 executes a clutch engagement control according to an individually provided process (subroutine). More particularly, as a basic manner, when the vehicle speed V SP is greater than a creep control threshold, the forward clutch 40 is engaged. When the vehicle speed V SP is smaller than the creep control threshold and when the throttle opening TVO is greater than a creep control full close threshold, the engagement of the forward clutch 40 is released. Such operations are executed by generating and outputting the corresponding signal S CL from the microcomputer 310 to the fourth drive circuit 314.
  • the gain for changing the duty ratio D/T CL is changed in inverse proportion to the difference between the engine revolution speed N E and the input rotation speed N Pri (turbine output shaft rotation speed).
  • the microcomputer 310 executes the control of the line pressure P L according to the process shown by a flowchart of Fig. 7. The detailed explanation of this line pressure control will be given later with reference to the flowchart of Fig. 7.
  • the microcomputer 310 executes a transmission ratio control according to an individually prepared process (subroutine). More particularly, with respect to the objective transmission ratio C R , the total number of the pulses and the number of pulses per a unit time are determined. Then, the microcomputer 310 generates and outputs the pulse control signal S S/M satisfying the both numbers. After the execution of the step S9, the routine of this program returns to the main program.
  • the microcomputer 310 sets a reference line pressure P L0 by executing a process shown in Fig. 8.
  • the microcomputer 310 sets a start line pressure P L1 by executing a process shown in Fig. 9.
  • the microcomputer 310 sets a slow decompression inhibiting flag F INHB and a slow decompression step amount ⁇ P L by executing a process shown in Fig. 10.
  • the microcomputer 310 sets a quick acceleration line pressure P L2 by executing a process shown in Fig. 11.
  • the microcomputer 310 sets a brake line pressure P L3 by executing a process shown in Fig. 12.
  • the microcomputer 310 sets a downshift line pressure P L4 by executing a process shown in Fig. 13.
  • the microcomputer 310 sets an objective line pressure P LOR by executing a process in Fig. 14.
  • the microcomputer 310 calculates a line pressure duty ratio D/T PL for achieving the objective line pressure P LOR .
  • the microcomputer 310 At a step S19, the microcomputer 310 generates and outputs a line pressure control signal according to the line pressure control duty ratio D/T PL according to an individually provided process. Then, the routine returns to the step S9 of Fig. 3.
  • a control map employed in a known duty ratio control may be applied to the control map for the line pressure control duty ratio D/T PL .
  • a known PWM (Pulse Width Modulation) control may be employed in the generation of the line pressure control signal S PL according to the line pressure control duty ratio D/T PL .
  • the microcomputer 310 calculates a torque ratio t according to the torque converter input and output speed ratio N E /N Pri and an individually provided process including a retrieval of the control map. More particularly, the microcomputer 310 calculates the torque converter input/output speed ratio N E /N Pri by dividing the engine revolution speed N E by the input rotation speed N Pri . Then, the microcomputer 310 determines whether the torque converter 12 is put in a lockup state or an unlockup (converter) state with reference to the map shown in Fig. 15 according to the torque converter input/output speed ratio N E /N Pri . When the torque converter 12 is put in the unlock state (converter state), the microcomputer 310 obtains the torque ratio t according to the torque converter input/output speed ratio N E /N Pri .
  • the microcomputer 310 calculates the reference line pressure P L0 from the input torque T Pri and the transmission ratio C P according to the control map of Fig. 16. Thereafter, the routine proceeds to the step S12 of Fig. 7.
  • the control map of Fig. 16 is a map for setting the reference line pressure P L0 according to the input torque T Pri and the present transmission ratio C P . Since the line pressure P L corresponds to the belt holding force, it is preferable to possibly keep the line pressure P L small in view of the durability of the belt 24 and the energy efficiency of the CVT.
  • the belt 24 is required to transmit the torque between the driver and follower pulleys 16 and 26, it is necessary to control the line pressure P L so as to prevent the belt 24 from slipping on the pulleys. That is, it is necessary to apply a necessary line pressure to the pulleys 16 and 26 to hold the belt 24 thereby.
  • the torque to be transmitted by the CVT is increased according to the increase of the transmission ratio C P or the increase of the input torque T Pri
  • the reference line pressure P L0 is set only by the transmission ratio C P and the input torque T Pri .
  • the microcomputer 310 determines whether or not the previous value S RANGE(n-1) of the shift range signal is a non-running range such as N-range or P-range. When the determination at the step S201 is affirmative, the routine proceeds to a step 5202. When the determination at the step S202 is negative, the routine jumps to a step S203.
  • the microcomputer 310 determines whether or not the present value S RANGE(n) of the shift range signal is a running range such as D-range, 2-range, L-range or R-range. When the determination at the step S202 is affirmative, the routine proceeds to a step S204. When the determination at the step S202 is negative, the routine jumps to a step S203.
  • the routine proceeds to a step S205 wherein the microcomputer 310 sets the start control counter CNT 1 at a predetermined start control value CNT STT . Thereafter, the routine proceeds to the step S203.
  • the microcomputer 310 determines whether the start control flag F STT is set at 1 or not. When the determination at the step S203 is affirmative, the routine proceeds to a step S206. When the determination at the step S203 is negative, the routine jumps to a step S207.
  • step S208 the microcomputer 310 determines whether or not the start control flag F STT is smaller than or equal to 0.
  • the routine proceeds to a step S207.
  • the routine proceeds to a step S209.
  • step S210 the microcomputer 310 sets the start line pressure P L1 at 0 (P L1 ⁇ 0 (MPa)).
  • the microcomputer 310 set the start line pressure PL1 at a predetermined start value P LSTT .
  • the microcomputer 310 determines whether the start control flag F STT is set at 0 or not. When the determination at the step S301 is affirmative, the routine proceeds to a step S302. When the-determination at the step S301 is negative, the routine jumps to a step S303.
  • the microcomputer 310 determines whether the anti-skid control system is put in an inoperative state or not. When the determination at the step S302 is affirmative, the routine proceeds to a step S304. When the determination at the step S302 is negative, the routine jumps to the step S303.
  • step S305 the microcomputer 310 sets the slow decompression step amount ⁇ P L according to the transmission ratio C P and the control map of Fig. 17.
  • the control map of Fig. 17 is provided for determining the pressure reduced amount with respect to each increasingly corrected line pressure P L1 to P L4 which is executed at a sampling time period ⁇ T.
  • the pressure reduced amount is the slow decompression step amount ⁇ P L which is decreased according to the increase of the transmission ratio C P and increased according to the decrease of the transmission ratio C P .
  • the microcomputer 310 sets the slow decompression step amount ⁇ P L at a preset maximum value ⁇ P LMAX .
  • a step S401 the microcomputer 310 determines whether the quick acceleration flag F ACC is set at 0 or not. When the determination at the step S401 is affirmative, the routine proceeds to a step S402. When the determination at the step S401 is negative; the routine jumps to a step S403.
  • the microcomputer 310 determines whether or not an acceleration pedal is quickly depressed (the quick acceleration is executed) by executing an individually provided calculation process such as a determination process as to whether the throttle opening TVO is largely and quickly changed.
  • the routine proceeds to a step S404.
  • the routine jumps to the step S403.
  • the microcomputer 310 sets the quick acceleration control counter CNT 2 at a predetermined quick acceleration control value CNT ACC (CNT 2 ⁇ CNT ACC ).
  • the microcomputer determines whether or not the quick acceleration flag F ACC is set at 1.
  • the routine proceeds to a step S403.
  • the routine jumps to a step S407.
  • the microcomputer 310 determines whether or not the quick acceleration control counter CNT 2 is smaller than or equal to 0. When the determination at the step S408 is affirmative, the routine proceeds to a step S409. When the determination at the step S408 is negative, the routine jumps to a step S410.
  • step S411 the microcomputer 310 determines whether or not the slow decompression inhibiting flag F INHB is set at 0.
  • the routine proceeds to a step S412.
  • step S411 the routine jumps to the step S407.
  • the microcomputer 310 decreases the quick acceleration line pressure P L2 by a predetermined slow decompression step amount ⁇ P L and sets the decreased value as the quick acceleration line pressure P L2 (P L2 ⁇ P L2 - ⁇ P L )
  • the microcomputer 310 determines whether or not the quick acceleration line pressure P L2 is higher than or equal to 0.
  • the routine proceeds to a step S414.
  • the routine jumps to the step S407.
  • the microcomputer 310 sets the calculated quick acceleration line pressure P LZ as it is (P L2 ⁇ P L2 ).
  • the microcomputer 310 sets 0 as the quick acceleration line pressure P L2 (P L2 ⁇ 0).
  • the microcomputer 310 sets the predetermined quick acceleration value P LACC as the quick acceleration line pressure (P L2 ⁇ P LACC ).
  • the microcomputer 310 determines whether or not a brake pedal is now depressed. More particularly, by detecting whether a brake switch is turned ON or OFF and by executing individual processing according to the condition of the brake switch, the microcomputer 310 determines whether or not the baking is now executed. When the determination at the step S501 is affirmative, the routine proceeds to a step S502. When the determination at the step S501 is negative, the routine proceeds to a step S503.
  • step S504 the microcomputer 310 determines whether or not a quick braking is executed. That is, it is determined whether or not the bake pedal is largely and quickly depressed. It will be understood that if a quick brake assist system is employed in a vehicle comprising the control system according to the present invention the determination as to the quick braking may be executed by determining whether the quick brake assist system is operated or not.
  • the routine proceeds to a step S505.
  • the routine proceeds to a step S506.
  • step S505 After the execution of the step S505 or S506, the routine proceeds to a step S507.
  • step S508 the microcomputer 310 determines whether or not the brake control counter CNT BRK is smaller than or equal to a predetermined value CNT BRK0 .
  • the routine proceeds to a step 5509.
  • the routine proceeds to a step S510.
  • the microcomputer 310 determines whether or not the vehicle speed V SP is greater than or equal to a predetermined low speed value V SP0 .
  • the routine proceeds to the step S507.
  • the routine proceeds to the step S510.
  • the microcomputer 310 determines whether or not the brake control flag F BRK is equal to 1. When the determination at the step S507 is affirmative, the routine proceeds to a step S511. When the determination at the step 5507 is negative, the routine proceeds to a step S512.
  • the microcomputer 310 determines whether or not the quick brake control flag F P.BRK is equal to 1. When the determination at the step S512 is affirmative, the routine proceeds to a step S513. When the determination at the step S512 is negative, the routine proceeds to a step S514.
  • step S515 the microcomputer 310 determines whether or not the slow decompression control inhibition flag F INHB is equal to 0.
  • the routine proceeds to a step S516.
  • the routine proceeds to the step S514.
  • the microcomputer 310 decreases the brake line pressure P L3 by the slow decompression step amount ⁇ P L and sets the subtracted brake line pressure at the brake line pressure P L3 (P L3 ⁇ P L3 - ⁇ P L ).
  • step S517 the microcomputer 310 determines whether or not the brake line pressure is greater than or equal to 0.
  • step S518 the routine proceeds to a step S518.
  • step S518 the routine proceeds to the step S518.
  • the microcomputer 310 sets the brake line pressure P L3 at 0 (P L3 ⁇ 0). After the execution of the step S514, the routine returns to the step S6 of Fig. 7.
  • the microcomputer 310 maintains the brake line pressure P L3 (P L3 ⁇ P L3 ). After the execution of the step S518, the routine returns to the step S16 of Fig. 7.
  • the microcomputer 310 sets the brake line pressure P L3 at a predetermined large brake value P LBRK (P L3 ⁇ P LBRK ). After the execution of the step S511, the routine returns to the step S16 of Fig. 7.
  • the microcomputer 310 sets the brake line pressure P L3 at a predetermined further large value P LP.LBRK (P L3 ⁇ P LP.LBRK ). After the execution of the step S513, the routine returns to the step S16 of Fig. 7.
  • the microcomputer 310 determines whether an upshift is executed or not, by executing an individual processing for determining whether the transmission ratio of a present shift range is smaller than that of a previous shift range or not.
  • the routine proceeds to a step S602.
  • the routine jumps to a step S603.
  • the microcomputer 310 determines whether a quick upshift such as a two-steps upshift is executed or not, by determining, for example, whether the present shift range is D-range with respect to a fact that the previous shift range is the L-range.
  • a quick upshift such as a two-steps upshift is executed or not, by determining, for example, whether the present shift range is D-range with respect to a fact that the previous shift range is the L-range.
  • the routine proceeds to a step S604.
  • the routine proceeds to a step S605.
  • the microcomputer 310 determines whether a quick downshift control flag F F.D.S is set at 1 or not. When the determination at the step S605 is affirmative, the routine proceeds to a step S606. When the determination at the step S605 is negative, the routine proceeds to the step S604.
  • the routine proceeds to the step S603 wherein the microcomputer 310 determines whether a downshift is executed or not, by executing an individual processing for determining whether a transmission ratio of a present shift range is greater than that of a previous shift range or not.
  • the routine proceeds to a step S607.
  • the routine jumps to a step S608.
  • the microcomputer 310 determines whether a quick downshift such as a two-steps downshift is executed or not, by determining, for example, whether the present shift range is L-range with respect to a fact that the previous shift range is D-range.
  • a quick downshift such as a two-steps downshift is executed or not, by determining, for example, whether the present shift range is L-range with respect to a fact that the previous shift range is D-range.
  • the routine proceeds to a step S609.
  • the routine proceeds to a step S610.
  • the microcomputer 310 determines whether the special upshift control flag F U.S is set at 0 or not. When the determination at the step S610 is affirmative, the routine proceeds to a step S611. When the determination at the step S610 is negative, the routine proceeds to the step S609.
  • the routine proceeds to the step S608 wherein the microcomputer 310 determines whether the present transmission ratio C P is equal to the goal transmission ratio C D or not.
  • the routine proceeds to a step S612.
  • the routine proceeds to a step S613.
  • step S614 the microcomputer 310 determines whether the slow decompression inhibiting flag F INHB is set at 0 or not.
  • the routine proceeds to a step S615.
  • the routine proceeds to a step S616.
  • the microcomputer 310 determines whether the special upshift control flag F U.S is set at 0 or not. When the determination at the step S616 is affirmative, the routine proceeds to a step S617. When the determination at the step S616 is negative, the routine jumps to a step S618.
  • the microcomputer 310 decreases the downshift line pressure P L4 by the slow decompression step amount ⁇ P L and stores the decreased downshift line pressure as the downshift line pressure P L4 (P L4 ⁇ P L4 - ⁇ P L ).
  • step S619 the microcomputer 310 determines whether the special upshift control flag F U.S is set at 0 or not.
  • the routine proceeds to a step S620.
  • the routine proceeds to a step S621.
  • the microcomputer 310 determines whether or not the downshift line pressure P L4 is greater than or equal to a predetermined relatively large downshift value P LD.S .
  • the routine proceeds to the step S620.
  • the routine proceeds to the step S618.
  • the microcomputer 620 determines whether or not the newly calculated downshift line pressure P L4 is greater than or equal to 0 (MPa). When the determination at the step S620 is affirmative, the routine proceeds to a step S622. When the determination at the step S622 is negative, the routine proceeds to the step S617.
  • the microcomputer 310 sets the downshift line pressure P L4 at 0 (P L4 ⁇ 0). Then, the routine returns to the step S17 of Fig. 7.
  • the microcomputer 310 maintains the downshift line pressure P L4 as it is (P L4 ⁇ P L4 ). Then, the routine returns to the step S17 of Fig. 7.
  • the microcomputer 310 determines whether the downshift control flag F D.S is set at 0 or not.
  • the routine proceeds to a step S623.
  • the routine proceeds to a step S624.
  • the microcomputer 310 determines whether the special upshift control flag F U.S is set at 0 or not. When the determination at the step S623 is affirmative, the routine proceeds to the step S618. When the determination at the step S623 is negative, the routine jumps to the step S614.
  • the microcomputer 310 sets the downshift line pressure P L4 at the predetermined downshift value P LD.S (P L4 ⁇ P LD.S ). Then, the routine returns the step S7 of Fig. 7.
  • the microcomputer 310 sets the downshift line pressure P L4 at a predetermined large downshift value P LF.D.S which is further larger than the predetermined downshift value P LD.S (P L4 ⁇ P LF.D.S ). Then, the routine returns the step S17 of Fig. 7.
  • the microcomputer 310 determines whether or not the vehicle speed V SP is smaller than or equal to a predetermined start speed V SPL0 .
  • the routine proceeds to a step S702.
  • the routine proceeds to a step S703.
  • the microcomputer 310 sets the objective line pressure P LOR at the start line pressure P L1 (P L0R ⁇ P L1 ).
  • step S704 the microcomputer 310 determines whether all of the start control flag F STT , the quick acceleration control flag F ACC , the brake control flag F BRK , the quick brake control flag F P.BRK , the downshift control flag F D.S and the quick downshift control flag F F.D.S are 0 or not.
  • the routine proceeds to a step S705.
  • the routine proceeds to a return step from which the routine proceeds to the step S18 of Fig. 7.
  • the microcomputer 310 determines whether the objective line pressure P LOR is smaller than or equal to the reference line pressure P L0 . when the determination at the step S705 is affirmative, the routine proceeds to a step S706. When the determination at the step S705 is negative, the routine jumps to the return step.
  • the microcomputer 310 set the objective line pressure P LOR at the reference line pressure P LO (P LOR ⁇ P LO ). Then, the routine proceeds to the return routine to proceed to the step S18 of Fig. 7.
  • the reference line pressure P L0 generates a belt holding force to prevent the slippage of the belt which receives a power obtained by converting the input torque T Pri (the multiple of the engine torque T E and the torque ratio t) by the transmission ratio. Therefore, the reference line pressure P L0 is not basically related with the change of the load of the output system. That is, only the right direction input load may be taken in account of the reference line pressure P L0 .
  • the routine proceeds from the step S411 to the step S412 wherein the previous quick acceleration line pressure P L2 is decreased by the slow decompression step amount ⁇ P L (P L2 ⁇ P L2 - ⁇ P L ). Until the new quick acceleration line pressure P L2 is smaller than or equal to 0, the affirmative determination at the step S413 is repeated. Therefore, the quick acceleration line pressure P L2 is decreased by the step amount ⁇ P L at each sampling time period, ⁇ T.
  • the routine proceeds from the step S413 to the step S407 wherein the quick acceleration line pressure P L2 is held at 0. That is, the quick acceleration line pressure P L2 is steppingly increased when the acceleration pedal is quickly depressed and is then held at the predetermined value P LACC for a predetermined time period CNT ACC . Thereafter, it is gradually decreased and is held at 0 (MPa).
  • the routine proceeds from the step S515 to the step S516 wherein the previous brake line pressure P L3 is decreased by the slow decompression step amount ⁇ P L .
  • the determination at the step S517 is affirmative, and therefore the routine proceeding from the step S517 to the step S518 is repeated. Accordingly, the brake line pressure P L3 is decreased by the slow decompression step amount ⁇ P L at each sampling time period.
  • this reduced brake line pressure P L3 becomes smaller than 0 (Mpa)
  • the brake line pressure P L3 is held at 0 (P L3 ⁇ 0) because the determination at the step S517 becomes negative and the routine proceeds from the step S517 to the step S514.
  • the brake line pressure P L3 is steppingly increased during the operation of the brake pedal and reaches the predetermined value P LBRK or the predetermined quick brake value P LP.BRL . After the cancellation of the braking operation, the increased brake line pressure P L3 is held for the predetermined time period CNT BRK0 . Thereafter, it is gradually decreased and is held at 0 (MPa).
  • the downshift line pressure P L4 is held at the predetermined relatively large value P LD.S .
  • the routine repeatingly proceeds from the step S613 through the step S624 to the step S626. Therefore, the downshift line pressure P L4 is held at the predetermined further large value P LF.D.S .
  • the routine proceeds from the step S614 to the step S615 wherein the previous downshift line pressure P L4 is decreased by the slow decompression step amount ⁇ P L .
  • the downshift line pressure P L4 is set to be decreased by the slow decompression step amount ⁇ P L at each sampling time period ⁇ T.
  • the routine proceeds from the step S620 to the step S617 wherein the downshift line pressure P L4 is held at 0 (MPa) (P L4 ⁇ 0). That is, the downshift line pressure P L4 is steppingly increased to the predetermined downshift value P LD.S or the predetermined quick downshift value P LP.BRK during the downshift operation. Further, the downshift line pressure P L4 is held until the shifting is completed. Thereafter, the downshift line pressure P L4 is gradually decreased and held at 0 (MPa).
  • the routine proceeds to the step S602 wherein it is determined whether the quick upshift is executed.
  • the routine proceeds to the step S604 wherein all control flags in this minor program are reset.
  • the quick downshift control flag F F.D.S is set, that is, when the quick downshift operation has been executed previously and when the shifting is not yet completed, the shift position is upshifted by one step.
  • the routine proceeds to the step S618 wherein the special upshift control flag F U.S is reset. Thereafter, the downshift line pressure P L4 is held at the predetermined downshift value P LD.S .
  • the minor program of Fig. 14 for setting the objective line pressure P LOR is executed. Even if the start line pressure P L1 has been set, substantially the set condition is the same.
  • the routine proceeds from the step S701 to the step S703 wherein the maximum value among the set line pressures P L1 , P L2 , P L3 , P L4 is once set as the objective line pressure P LOR .
  • the routine proceeds through the steps S704 and S705 to the step S706 wherein the objective line pressure P LOR is set at the reference line pressure P L0 . That is, when the set line pressures P L1 to P L4 except for the reference line pressure P L0 is set according to the vehicle condition, the maximum value among them is basically set as the objective line pressure P LOR so as to set the line pressure P L for preventing the generation of the slippage of the belt according to the condition.
  • the objective line pressure P LOR is set at the reference line pressure P L0 . This enables the line pressure for preventing the slippage of the belt against the input load from the engine to be supplied.
  • the objective line pressure P LOR is held at the predetermined value for a predetermined time period and then slowly decreased by the slow decompression step amount ⁇ P L , as shown in Figs. 18A and 18B.
  • the objective line pressure P LOR is converged into a predetermined value such as the reference line pressure P L0 although in each minor program it is converged into 0 (MPa) and practically is converged into the reference line pressure P L0 .
  • the fluctuation of the friction between the belt and the pulleys tends to cause the vibrations of the drive system.
  • Such vibrations tend to become large when the transmission ratio C P is large since the fluctuation of the acceleration becomes large according to the increase of the transmission ratio C P . Therefore, in the control map used in the step S305, the slow decompression step amount ⁇ P L is deceased according to the increase of the transmission ratio C P .
  • a time constant for controlling the achievement time with respect to the objective value may be employed in setting the decompression speed. That is, in this case, by setting the time constant ⁇ so as to become larger according to the increase of the transmission ratio C P , the decompression speed is decreased.
  • the routine proceeds to the step S205 wherein the start control counter CNT 1 is set at the predetermined value CNT STT .
  • the routine proceeds from the step S203 to the step S206 wherein the start control counter CNT 1 is decreased by 1. Until the start control counter CNT 1 becomes smaller than or equal to 0, the negative determination at the step S208 is repeated.
  • the start line pressure P L1 is held at the predetermined value P LSTT set at the step S209.
  • the start line pressure P L1 is set at 0 in a breath (P L1 ⁇ 0). That is, when the shift range is changed from the N-range to the D-range, the start line pressure P L1 is steppingly increased and is held at the predetermined value P LSTT for the predetermined time period CNT STT . Thereafter, the start line pressure P L1 is quickly decreased and held at 0 (MPa).
  • start line pressure P L1 When the start line pressure P L1 is set by the above-mention manner and is greater than the other set line pressure P L2 to P L4 , the start line pressure P L1 is treated as the objective line pressure P LOR .
  • the start line pressure P L1 When the vehicle speed V SP is smaller than or equal to the predetermined start value V SPL0 , the start line pressure P L1 is forcibly treated as the objective line pressure P LOR .
  • the clutch pressure P CL is 0 (MPa). Under this condition, if the running range such as D-range is selected, the clutch pressure P C is quickly increased to quickly and smoothly engage the start clutch such as the forward clutch 40 and the reverse brake 50. On the other hand, the clutch pressure P CL is produced from the branch pressure of the line pressure P L , the clutch pressure P CL is quickly increased by setting the line pressure at a some increased value. Therefore, when the starting shift range is selected, the start line pressure P L1 is correctly increased at the predetermined value P LSST for the predetermined time period CNT STT so as to increase the line pressure P L .
  • the start line pressure P L1 is set as the objective line pressure P LOR in advance with others.
  • the start line pressure P L1 is set to quickly increase the clutch pressure P CL , and not to correspond to the phenomenon that the input load to the CVT mechanism 29 is temporally increased. This corresponds to the rise-up condition of the clutch pressure P CL shown in Figs. 19A and 19B. Therefore, as shown by alternate two dots and dash line of Fig. 19B, when the start line pressure P L1 is slowly decompressed after the predetermined time period elapsed as is similar to the other set line pressures P L2 to P L4 , the clutch pressure P CL becomes greater than the objective value P CL0 due to the increased amount from the line pressure such as the reference line pressure P L0 . This quick engagement of the forward clutch 40 may produce the vibrations of the drive system.
  • the present embodiment according to the present invention is arranged, for example, to quickly decompress the start line pressure P L1 to 0 MPa after the predetermined time period CNT STT for adjusting the clutch pressure P CL at the objective value P CL0 , as shown by a continuous line in Fig. 19A so as to prevent the generation of the vibrations of the start clutch.
  • the present embodiment according to the present invention is arranged such that when the start control flag F STT is set the routine proceeds from the step S301 to the step 5303 wherein the slow decompression inhibit flag F INHB is set, and at the step S603 the slow decompression step amount ⁇ P L is set at the predetermined maximum value ⁇ P LMAX .
  • step S11 proceeds promptly from the step S411 to the step S407 after the predetermined time period CNT ACC elapsed.
  • the quick acceleration line pressure P L2 is set at 0 (MPa).
  • the routine in the processing of Fig. 12 after the predetermined time period CNT BRK0 elapsed the routine proceeds promptly from the step S515 to the step S514 wherein the brake line pressure P L3 is set at 0 (MPa).
  • the routine proceeds promptly from the step S614 to the step S617 wherein the downshift line pressure P L4 is set at 0 (MPa).
  • the set line pressures P L2 to P L4 are correctly increased at the respective predetermined values and are then rapidly decompressed so that the start line pressure P L1 is easily achieved. Further, when the slow decompression inhibit flag F INHB and the special upshift control flag F U.S are set, the routine in the processing of Fig. 14 proceeds from the step S614 through the steps S616 and S618 to the step S625 wherein the predetermined downshift value P LD.S is rapidly achieved.
  • the increased amount of the friction according to the slow decompression of the set line pressures P L2 to P L4 affects the anti-skid control. That is, the anti-skid control is generally executed by decompressing the wheel cylinder pressure of the wheel put in the locked or locking (tend to lock) condition to decrease the braking force to the wheel and thereby increasing the balance of the road surface reaction torque to increase the wheel speed.
  • the friction is large due to the slow decompression of the set line pressures P L2 to P L4 as shown by the alternate two-dots and dash line of Figs. 20A and 20B, the increased amount of the friction functions to prevent the wheel speed V WDi from increasing. This degrades the responsibility of the control.
  • the present embodiment according to the present invention is arranged to communicate the transmission control unit 300 and the anti-skid control unit 500 with each other. Further, when the anti-skid control is active, the routine of Fig. 10 proceeds from the step S302 to the step S303 wherein the slow decompression inhibit flag F INHB is set. Therefore, after the setting thereof the set line pressure P L2 to P L4 are not decompressed slowly and decompressed promptly to the original line pressure P L as shown by a continuous line of Fig. 20B. Therefore, the wheel speed V WDi is rapidly recovered to the increased speed, and the responsibility of the anti-skid control is ensured.
  • the line pressure duty valve 120 constitutes the CVT mechanism pressure control valve according to the present invention.
  • the step S12 and the step S209 of Fig. 9, the step S410 of Fig. 11, the steps S511 and S513 of Fig. 12, the steps S625 and the S626 of Fig. 13 executed in the steps S14 to S17 of Fig. 7 constitute a pressure increasing means.
  • the step S305 of Fig. 10, the step S406 of Fig. 11, the step S516 of Fig. 12 and the step S615 of Fig. 13 executed in the steps S13 to S17 of Fig. 7 constitutes a slow decompressing means.
  • the forward clutch 40, the reverse brake 50 and the clutch engagement control duty valve 129 constitute a start clutch engaging means.
  • the step S204 of Fig. 9, the step S301 and S303 of Fig. 10, the step S411 of Fig. 11, the step S515 of Fig. 12 and the step S614 of Fig. 13 constitute a clutch engagement quick decompressing means.
  • the steps S302 and S303 of Fig. 10, the step S411 of Fig. 11, the step S515 of Fig. 12 and the step S614 of Fig. 13 constitute a braking force quick decompressing means.
  • control unit thereof is constituted by a microcomputer
  • a combination of electronic circuits such as calculating circuits may be employed in the control unit instead of the microcomputer.

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  • Engineering & Computer Science (AREA)
  • General Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Control Of Transmission Device (AREA)
  • Control Of Driving Devices And Active Controlling Of Vehicle (AREA)
  • Regulating Braking Force (AREA)

Claims (15)

  1. Steuerungssystem für ein stufenloses Getriebe (29) eines Fahrzeugs, wobei das stufenlose Getriebe (29) eine Antriebsriemenscheibe (16), eine angetriebene Riemenscheibe (26) und einen Riemen (24) umfasst, der die Riemenscheiben miteinander verbindet, wobei das stufenlose Getriebe (29) ein Übersetzungsverhältnis verändert, indem es effektive Durchmesser der Riemenscheiben (16, 26) ändert, wobei das Steuersystem umfasst:
    eine Leitungsdruck-Ausübungseinrichtung (100), die einen Leitungsdruck entsprechend einer Eingangslast von dem Motor (10) auf das stufenlose Getriebe (29) auf die Riemenscheiben (16, 26) ausübt;
    eine Fahrzeugzustand-Erfassungseinrichtung (303, 304, 500, 505), die einen Zustand des Fahrzeugs erfasst;
    eine Einrichtung (300) zum Bestimmen eines temporären Anstiegs, die entsprechend dem erfassten Fahrzeugzustand bestimmt, dass die Eingangslast temporär erhöht ist;
    eine Druckerhöhungseinrichtung (300), die den Leitungsdruck temporär erhöht, wenn die Eingangslast temporär erhöht ist; und
    eine Einrichtung (300) zum langsamen Druckablassen, die den temporär erhöhten Leitungsdruck langsam ablässt,
    dadurch gekennzeichnet, dass:
    die Einrichtung (300) zum langsamen Druckablassen eine Druckablassgeschwindigkeit, die eine Geschwindigkeit des Ablassens des erhöhten Drucks anzeigt, mit einem Anstieg des Übersetzungsverhältnisses des stufenlosen Getriebes (29) verringert.
  2. Steuerungssystem nach Anspruch 1, das des Weiteren umfasst:
    eine Anfahrkupplungs-Einrückeinrichtung, die eine Anfahrkupplung (40; 50) einrückt, indem sie einen Abzweigdruck des Leitungsdrucks über ein Kupplungseinrück-Steuerventil steuert, wobei die Druckerhöhungseinrichtung (300) den Leitungsdruck temporär erhöht, wenn die Anfahrkupplung (40; 50) durch die Anfahrkupplungs-Einrückeinrichtung eingerückt wird; und
    eine Einrichtung (300) zum schnellen Druckablassen, die den Leitungsdruck schnell ablässt, wenn der Leitungsdruck in einem Anfahrkupplungs-Einrückzustand erhöht ist, und wenn der Leitungsdruck abgelassen wird.
  3. Steuerungssystem nach Anspruch 1, das des Weiteren umfasst:
    eine Antischlupf-Steuerungseinrichtung, die eine Radgeschwindigkeit eines Antriebsrades erhöht, indem sie eine durch einen Bremszylinder für ein Antriebsrad erzeugte Bremskraft verringert; und
    eine Einrichtung (300) zum schnellen Druckablassen, die den Leitungsdruck schnell ablässt, wenn die Antischlupf-Steuerungseinrichtung die Bremskraft verringert und wenn der durch die Druckerhöhungseinrichtung erhöhte Leitungsdruck abgelassen wird.
  4. Steuerungssystem nach einem der Ansprüche 1 bis 3, wobei die Fahrzeugzustand-Erfassungseinrichtung (303, 304, 500, 505) einen Drosselöffnungssensor (303), der eine schnelle Beschleunigung des Fahrzeugs erfasst, einen Bremsschalter (505), der einen Bremsvorgang erfasst, einen Verzögerungsschalter (304), der ein Anfahren des Fahrzeugs erfasst, und eine Antischlupf-Steuerungsvorrichtung (500) enthält, die über eine Betätigung einer Antischlupf-Steuerung informiert.
  5. Steuerungssystem nach Anspruch 4, wobei die Einrichtung (300) zum Bestimmen einer temporären Erhöhung einen Mikrocomputer (210) enthält, der entsprechend Signalen von dem Drosselöffnungssensor (303), dem Bremsschalter (505) und dem Verzögerungsschalter (304) bestimmt, dass die Eingangslast erhöht ist.
  6. Steuerungssystem nach Anspruch 5, wobei die Druckerhöhungseinrichtung (300) einen Mikrocomputer enthält, der entsprechend der Bestimmung der Einrichtung (300) zum Bestimmen einer temporären Erhöhung ein Steuersignal, das einen temporär erhöhten Leitungsdruck anzeigt, an die Leitungsdruck-Ausübungseinrichtung (100) ausgibt.
  7. Steuerungssystem nach einem der Ansprüche 1 bis 6, wobei die Einrichtung (100) zum langsamen Druckablassen einen Mikrocomputer (310) enthält, der ein Steuersignal ausgibt, um den erhöhten Leistungsdruck um ein Druckablass-Schrittmaß in vorgegebenen Intervallen langsam auf einen normalen Leitungsdruck zu verringern.
  8. Steuerungssystem nach einem der Ansprüche 1 bis 7, das des Weiteren eine Pumpe (101) umfasst, die Druck auf das dem stufenlosen Getriebe (29) zuzuführende Fluid ausübt.
  9. Steuerungssystem nach Anspruch 1, das des Weiteren umfasst:
    eine Leitungsdruck-Steuerungseinrichtung (310), die einen auf die Riemenscheiben (16, 26) ausgeübten Leitungsdruck entsprechend einer Eingangslast von dem Motor (10) steuert;
    eine Einrichtung (300) zum Entscheiden über eine temporäre Erhöhung, die entsprechend dem erfassten Fahrzeugzustand entscheidet, dass die Eingangslast temporär erhöht ist;
    eine Druckablassgeschwindigkeits-Bestimmungseinrichtung (300), die eine Druckablassgeschwindigkeit entsprechend dem erfassten Fahrzeugzustand bestimmt; und
    eine Druckablasseinrichtung (300), die den temporär erhöhten Leitungsdruck mit der Druckablassgeschwindigkeit ablässt.
  10. Steuerungssystem nach Anspruch 9, wobei der Fahrzeugzustand das Übersetzungsverhältnis des stufenlosen Getriebes (29) einschließt und die Druckablassgeschwindigkeit entsprechend der Erhöhung des ausgewählten Übersetzungsverhältnisses verringert wird.
  11. Steuerungssystem nach einem der Ansprüche 1 bis 10, wobei die Fahrzeugzustand-Erfassungseinrichtung einen Eingangsdrehzahl-Sensor (305) enthält, der einen Eingriff zwischen dem Motor (10) und dem stufenlosen Getriebe (29) erfasst.
  12. Steuerungssystem nach einem der Ansprüche 4 bis 11, wobei, wenn die Fahrzeugzustand-Erfassungseinrichtung (303, 304, 500, 505) erfasst, dass die Antischlupf-Steuerung nunmehr ausgeführt wird, die Druckablassgeschwindigkeit einen großen Wert annimmt.
  13. Steuerungssystem nach Anspruch 12, wobei, wenn der temporär erhöhte Leitungsdruck auf den normalen Leitungsdruck zurückgeführt wird, die Druckablassgeschwindigkeit einen kleinen Wert annimmt, der erheblich kleiner ist als der große Wert.
  14. Steuerungssystem nach Anspruch 10, wobei die Leitungsdruck-Steuerungseinrichtung ein Leitungsdruck-Steuerventil (120) ist.
  15. Steuerungssystem nach einem der Ansprüche 1 bis 14, wobei das stufenlose Getriebe (29) umfasst:
    eine Antriebsriemenscheibe (16), die mit einem Motor (10) des Fahrzeugs verbunden ist;
    eine angetriebene Riemenscheibe (26), die beim Ändern einer Eingangskraft an der Antriebsriemenscheibe (16) Kraft ausgibt.
EP98113895A 1997-07-25 1998-07-24 Steuersystem für stufenloses Getriebe Expired - Lifetime EP0893627B1 (de)

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JP200454/97 1997-07-25
JP20045497A JP3339370B2 (ja) 1997-07-25 1997-07-25 無段変速機の制御装置
JP20045497 1997-07-25

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EP0893627A2 EP0893627A2 (de) 1999-01-27
EP0893627A3 EP0893627A3 (de) 2001-02-28
EP0893627B1 true EP0893627B1 (de) 2004-02-11

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JP3339370B2 (ja) 2002-10-28
US6030313A (en) 2000-02-29
DE69821557T2 (de) 2004-07-01
EP0893627A2 (de) 1999-01-27
JPH1144359A (ja) 1999-02-16
EP0893627A3 (de) 2001-02-28
DE69821557D1 (de) 2004-03-18

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